Conventionally, as disclosed in a Japanese laid-open patent publication No. 2011-31426, an elastic roller (a platen roller for example) has been used in a thermal printer, etc. A print paper is pinched between a thermal head and a platen roller with preset print pressure. Heat generation based on print data from the thermal head is utilized, and the print paper is fed with rotation of the platen roller driven. Accordingly, necessary information is printed on the print paper.
A circumferential length of the platen roller plays an important role in print quality of the print paper. More specifically, when wear volume of the platen roller is greater than a certain value, the diameter of the platen roller becomes small and accordingly the circumferential length of the platen roller becomes short.
Consequently, as wear of the platen roller proceeds with long term usage thereof, a length of a printed character becomes smaller. Thus, a problem arises that print accuracy is degraded.
In view of the above, when wear volume of the platen roller is greater than a certain value, it is required to replace the platen roller with a new one. Thus, an elastic roller has been demanded with which one can control limit of print accuracy or print quality.
However, it is virtually impossible to visually observe wear volume of a platen roller. Thus, there is a problem that it is difficult for a user of the platen roller to be aware of time for replacement thereof.
Incidentally, it is possible for a user to be indirectly aware of time for replacement of the platen roller by checking a calculation result of a feeding distance of a print paper based on a data amount for printing in a thermal printer. However, wear volume varies in accordance with a condition of usage of the thermal printer such as an ambient environmental condition around the thermal printer, print pressure, a kind of a print paper or an arrangement of a print paper. Thus, an elastic roller has been demanded with which one can directly and visually recognize wear volume of the elastic roller.
Further, because influence on print quality by variation of wear volume with usage of the platen roller is not even, a method has been demanded with which one can determine time for replacement of the platen roller in accordance with wear volume of the platen roller.
Needless to say, the same problem and the same demand exist not only in a platen roller but also in the other elastic roller.